Re: [Qemu-devel] [PATCH v6 07/11] migration: poll the cm event while wait RDMA work request completion

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Lidong Chen (jemmy858585@gmail.com) wrote:
> From: Lidong Chen <jemmy858585@gmail.com>
> 
> If the peer qemu is crashed, the qemu_rdma_wait_comp_channel function
> maybe loop forever. so we should also poll the cm event fd, and when
> receive RDMA_CM_EVENT_DISCONNECTED and RDMA_CM_EVENT_DEVICE_REMOVAL,
> we consider some error happened.
> 
> Signed-off-by: Lidong Chen <lidongchen@tencent.com>
> Signed-off-by: Gal Shachaf <galsha@mellanox.com>
> Signed-off-by: Aviad Yehezkel <aviadye@mellanox.com>

I found the doc in the man page for rdma_create_event_channel
that said 'Users may make the fd non-blocking, poll or select the fd,
etc', so:


Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  migration/rdma.c | 33 ++++++++++++++++++++++++++++++---
>  1 file changed, 30 insertions(+), 3 deletions(-)
> 
> diff --git a/migration/rdma.c b/migration/rdma.c
> index d6bbf28..673f126 100644
> --- a/migration/rdma.c
> +++ b/migration/rdma.c
> @@ -1489,6 +1489,9 @@ static uint64_t qemu_rdma_poll(RDMAContext *rdma, uint64_t *wr_id_out,
>   */
>  static int qemu_rdma_wait_comp_channel(RDMAContext *rdma)
>  {
> +    struct rdma_cm_event *cm_event;
> +    int ret = -1;
> +
>      /*
>       * Coroutine doesn't start until migration_fd_process_incoming()
>       * so don't yield unless we know we're running inside of a coroutine.
> @@ -1505,13 +1508,37 @@ static int qemu_rdma_wait_comp_channel(RDMAContext *rdma)
>           * without hanging forever.
>           */
>          while (!rdma->error_state  && !rdma->received_error) {
> -            GPollFD pfds[1];
> +            GPollFD pfds[2];
>              pfds[0].fd = rdma->comp_channel->fd;
>              pfds[0].events = G_IO_IN | G_IO_HUP | G_IO_ERR;
> +            pfds[0].revents = 0;
> +
> +            pfds[1].fd = rdma->channel->fd;
> +            pfds[1].events = G_IO_IN | G_IO_HUP | G_IO_ERR;
> +            pfds[1].revents = 0;
> +
>              /* 0.1s timeout, should be fine for a 'cancel' */
> -            switch (qemu_poll_ns(pfds, 1, 100 * 1000 * 1000)) {
> +            switch (qemu_poll_ns(pfds, 2, 100 * 1000 * 1000)) {
> +            case 2:
>              case 1: /* fd active */
> -                return 0;
> +                if (pfds[0].revents) {
> +                    return 0;
> +                }
> +
> +                if (pfds[1].revents) {
> +                    ret = rdma_get_cm_event(rdma->channel, &cm_event);
> +                    if (!ret) {
> +                        rdma_ack_cm_event(cm_event);
> +                    }
> +
> +                    error_report("receive cm event while wait comp channel,"
> +                                 "cm event is %d", cm_event->event);
> +                    if (cm_event->event == RDMA_CM_EVENT_DISCONNECTED ||
> +                        cm_event->event == RDMA_CM_EVENT_DEVICE_REMOVAL) {
> +                        return -EPIPE;
> +                    }
> +                }
> +                break;
>  
>              case 0: /* Timeout, go around again */
>                  break;
> -- 
> 1.8.3.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK